It is, of course, well known in the art to provide pads of paper in which each sheet of a stack constituting a pad is provided on its underside with a marginal strip of non-drying, slightly tacky adhesive, also known as repositionable or light tack adhesive. This allows each sheet to be lightly and temporarily bonded to other surfaces including, initially, the top surface of an underlying similar sheet in the pad. See, for example, the Swiss patent to Eugster 452,479 dated May 31, 1986. The present assignee makes and sells under the NOTE-STIX.RTM. name several varieties of note pads of the type described above.
It is also well known particularly in the business forms art, to provide multiple sheet business forms with carbonless (self-imaging) coatings for producing multiple copies of an original writing. See, for example, U.S. Pat. Nos. 3,981,523; 4,126,334 and 4,199,174, all assigned to the present assignee. Typical carbonless copying systems include a combination of adjacent cooperating CB and CF layers on adjacent sheets. For example, the bottom surface of the top sheet is typically coated with carbonless micro-capsules (the CB coating or layer) which burst upon the application of localized pressure, to transfer an image onto a resinous or clay coating (the CF coating or layer) provided on the top surface of a lower adjacent sheet. Other arrangements include a combined CB/CF coating on the top surface of the lower sheet, resulting in image transferal to the lower sheet upon original writing pressure applied to the top surface of the upper sheet. Combining the concepts of repositionable adhesives and carbonless coatings in a single system in a commercially acceptable format has yet to be achieved.
Attempts have been made, however, to combine carbonless copying with repositionable adhesive techniques, and these attempts are reflected in the patent literature. For example, in U.S. Pat. No. 4,583,776, there is disclosed a series of contact film type labels fastened together to form a label set. Each of the film labels is provided with light tack adhesive on one surface of the label, while disposed between the labels is a transfer film which allows a carbonizing image to be formed on the succeeding label. The patent discloses the use of separate adhesive and transfer layers, however, and does not represent a true combination of the concepts as in the present invention.
U.S. Pat. No. 4,798,401 also seeks to combine the concepts of repositionable adhesive and carbonless imaging. In this patent, separate layers of adhesive and transfer layers are utilized, and a divider is positionable beneath a selected number of sheets for blocking transfer of an image to the sheets underneath the divider.
U.S. Pat. No. 4,714,276 describes a pad provided with a stack of preprinted sheets, each sheet being serially connected to its neighboring sheets along a respective margin, by means of a strip of non-drying lightly tacky pressure sensitive adhesive. Discrete areas of one or more sheets within the pad also carry a regional coating of carbon type or carbonless pressure sensitive image transfer material adapted to produce on the respective underlying region of the upper surface of the respective next sheet an image of what is pressed onto the sheet from above.
In U.S. Pat. No. 4,593,935, a pad of stationery is provided which comprises a block of writing sheets, in combination with a copy sheet. The copy sheet has a first face which includes a CB coating while the second face has neither a CF coating nor a CB coating. The copy sheet is preferably provided atop the pad as a separately detachable sheet. Each of the writing sheets comprises an upper surface and a lower surface with the upper surface of each of the writing sheets comprising a CF coating. Thus, the copy sheet may be inserted between the uppermost one of the writing sheets and the next writing sheet with the first face of the copy sheet uppermost. Since no CF coating is adjacent disposed to a CB coating, no copy is made upon the next sheet in the pad. When it is desired to make a copy of a written record, the copy sheet is inserted between the uppermost one of the writing sheets and the next consequent writing sheet with the second face of the copy sheet uppermost. The CB coating of the copy sheet then lies adjacent to the CF coating of the next sheet in the pad and writing pressure upon the topmost writing sheet produces a copy in the underlying sheet.
In U.K. Patent 1,007,543, a pad of paper utilizing carbonless copy techniques is employed wherein selected surfaces of each sheet are located so as to prevent reproduction of certain information.
The present invention combines the concept of repositionable adhesive with pressure sensitive, non-carbonless copying in a manner which heretofore has not been available in commercially acceptable form.
In accordance with an exemplary embodiment of this invention, a pressure sensitive copying paper also has the capability of temporarily adhering to a substrate. More specifically, carbonless microcapsules which contain a colorless dye (the CB coating or layer) are blended with an acrylate type repositionable adhesive, then coated onto the lower or back surface of a sheet. The resultant sheet can be utilized as a regular repositionable adhesive sheet; however, when it is brought into contact with a carbonless image transfer material (e.g., a phenolic resin, clay coated or salicylic acid derivative) on an underlying sheet (the CF sheet) in a configuration normally associated with the pressure sensitive copying paper, an image can be formed on the CF sheet upon application of original writing pressure on the CB sheet. Image transfer thus occurs regardless of whether the original writing pressure is applied over an adhesive area on the underside of the CB sheet. Subsequently, the CB sheet can be pulled away from the CF sheet, and can be made to adhere to a different substrate in the usual manner of a repositionable note pad sheet. The presence of the elastic adhesive particles in the sheet further serve as an anti-offset material for the dye containing microcapsules.
Thus, in accordance with the broader aspects of the invention, there is provided a pressure sensitive carbonless copying system comprising a) a first sheet having front and back surfaces, the back surface coated with a composition including a pressure sensitive adhesive component and a carbonless microcapsule component; and b) a second sheet having front and back surfaces, the front surface coated with a carbonless image transfer material, and wherein the first sheet is temporarily adhered to the second sheet by means of the pressure sensitive adhesive component of the mixture.
In another aspect, the present invention relates to a pad comprising a plurality of note sheets, each note sheet having an upper surface and a lower surface, wherein at least a portion of the lower surface of each sheet is coated with a composition including a mixture having a pressure sensitive adhesive component and a microcapsule component; and wherein the upper surface of each sheet is at least partially coated with a carbonless image transfer material.
In still another aspect, the invention relates to a method of manufacturing a multi-part paper product having carbonless copying and repositionable adhesive properties comprising the steps of:
a) mixing a pressure sensitive adhesive component in slurry form with a carbonless microcapsule component, also in slurry form; PA1 b) coating at least a portion of an underside of at least a first sheet with the mixture from step (a); PA1 c) coating at least a portion of a top side of at least a second sheet with a carbonless image transfer material; and PA1 d) adhering the underside of the first sheet to the top side of the second sheet.
The invention is applicable to various kinds of form constructions including two part business forms and multi-sheet note pads. These are merely exemplary, and the invention is not be considered as limited to only those specific examples described herein.
The invention thus provides an effective carbonless copy/repositionable adhesive pad or form in a simple, cost effective manner which eliminates the prior requirement of separate carbonless/adhesive layers.
Other objects and advantages of the invention will become apparent from the detailed description which follows.